1. Field of the Invention
The present invention relates generally to a wafer processing system. More particularly, the present invention relates to an integrated chemical mechanical polishing (CMP) system including a CMP wafer polishing unit and a post-CMP cleaning unit coupled to the CMP wafer polishing unit.
2. Description of the Prior Art
Chemical mechanical polishing (CMP) techniques are used for planarizing material layers on a wafer in semiconductor industry. In chemical mechanical polishing, slurry is dispensed onto a polishing surface of a polishing pad. Relative movement between the polishing surface and the wafer produces a combined mechanical and chemical effect on the surface of the wafer. This process creates a highly level surface on the wafer.
Polishing slurry or slurry is the main component used in the CMP process. Typically, the slurry used in the CMP process consists mainly of colloidal silica suspended in deionized water or KOH solution. The slurry is frequently fed by an automatic slurry feeding system in order to ensure uniform wetting of the polishing pad and proper delivery of the slurry. Conventionally, the once-used slurry is received by a waste liquid receiver in the CMP tool, stored in a waste liquid tank, and then completely disposed of.
After CMP, the wafer is transferred to a cleaning unit and scrubbed with roller-shaped PVA (polyvinyl acetate) brushes. During scrubbing of the wafer, a base chemical such as tetramethyl ammonium hydroxide (TMAH) is simultaneously applied onto the surface of the wafer to be cleaned. However, the amount of usage of TMAH is huge and accounts for about 1.3˜1.5 USD per wafer. This makes it one of the major consumable cost factors in a CMP process. It would be advantageous to have an improved CMP system that is capable of reducing the cost of polishing each wafer.